Thousands of 420 enthusiasts are expected to smoke pot with strangers in the heart of Vancouver's financial district for a hazy celebration of marijuana culture on Saturday.

Huge crowds have gathered outside the Vancouver Art Gallery every Apr. 20 since 1997 to light up together at 4:20 p.m. Thanks to social media in recent years the number of attendees have skyrocketed, making the celebration one of the largest of its kind in North America.

The exact number of people floating in and out of the art gallery crowd remains hard to pin down, but 420 Vancouver event coordinator and Green Party election candidate Jodie Emery predicts the number to surpass the 20,000 people who showed up last year.

“This year could be even bigger since it’s a day off, weekend,” said Emery to The Huffington Post B.C. on Monday. "If it's rainy weather, the turnout will be lower than our estimate. But I'm sure there will be thousands of people, rain or shine."

For the curious, the origins of “420” remains a mystery and is a hotly debated among smokers.

According to one folk legend, “420” was started in the ‘70s by a group of high school students in California. Big fans of the Grateful Dead, their group of friends nicknamed “The Waldos” met at 4:20 p.m. every day to smoke pot, according to Huffington Post reporter Ryan Grim.

Last week, a survey from UNICEF revealed Canadian kids smoke more pot than anywhere else compared to other developed nations. Among 11, 13, and 15-year-old kids, 28 per cent said they smoked marijuana in the past year.

Who would have thought, eh?

CLARIFICATION: An earlier version stated a strong police presence would be present at the event. To clarify, a prominent Vancouver police presence is expected around the crowd's perimeter to guide traffic. This version has been updated.

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Where Do Kids Smoke The Most Pot?

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- 4.55 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.
All data from UNICEF'S Child Well-Being Index for 2013.

- 5.54 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 6.08 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 6.6 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 7 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 8.02 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 8.55 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 10.04 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 10.05 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 10.54 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 11.51 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 13.04 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 13.11 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 14.24 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 14.60 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 14.69 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 15 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 16.07 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 16.62 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 17.05 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 17.45 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 18 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 18.5 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 21.49 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 22.05 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 22.54 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 24.06 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 24.13 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.

- 28 per cent of children aged 11, 13 and 15 report having used marijuana in the last year.